METHOD OF FORMING A HOLE IN A HARD GROUND STRUCTURE

Abstract

A method of forming a hole in a hard ground structure including the step of obtaining a drill-bit with a turning axis having: a central portion and first and second axially spaced ends; and a plurality of protruding blades. Each blade has first and second ends, a first end portion, a second end portion, a middle portion, and a circumferentially facing leading portion. The circumferentially facing leading portion of each blade has at least one discrete hard cutter thereat. The method further includes the step of turning the drill-bit around its axis in a first direction so that the blades are advanced, circumferentially facing leading portion first, while pulling the drill-bit axially, with the first drill-bit end in a leading direction, through the hard ground structure to thereby cause the discrete cutters to cut the hard ground structure.

Description

BACKGROUND OF THE INVENTION

Field of the Invention

The subject matter disclosed generally relates to hole openers. In particular, the subject matter relates to drill-bits.

Background Art

Hole openers have long been used in the HDD (Horizontal Directional Drilling) industry as well as in any geological well drilling applications. Traditional hole openers consist of roller cones (built in varying configurations) designed to pound, cut and penetrate rock formations. These “roller-cone” rock bits have been in use since the first design was patented by Baker Hughes in 1909. Since then, the roller cone rock bit has evolved through numerous iterations. The concept, in its most basic of terms, consists of one or more metal toothed, cone shaped, bearing driven cutters that literally roll over the rock continuously while a drilling rig applies pressure or weight from above. As these cone cutters roll over the rock, the metal teeth pound, cut and chew up the rock, allowing the bit to slowly penetrate the formation. An example of a traditional roller-cone rock bit is shown in FIG. 1A.

Another example of a traditional hole opener is shown in FIGS. 1B and 1C. These hole openers are typically referred to as split bits or cone cutter reamers. Generally these hole openers define a rotation shaft around which there are provided two or more drilling cones.

Although such hole-openers/reamers have achieved considerable popularity and commercial success in the HDD application, they frequently experience failures and cause increasing job costs (which are a significant burden to drilling companies). For example, it is a common occurrence for drillers to lose cones from their split bit reamers. This happens for a variety of reasons—whether it is poor construction of the tool, overuse, or other extenuating circumstances. Cone loss is a constant and looming threat. Having this happen in a bore can be catastrophic. This causes the need for the drilling Company to either fish out the lost cone, and in some cases start the bore again from scratch. All of this is done at the cost of the drilling company.

There is therefore an ongoing need for an improved drilling bit which is durable and at the same time achieves a higher drilling speed and less failure.

SUMMARY OF THE INVENTION

In one form, the invention is directed to a method of forming a hole in a hard ground structure. The method includes the steps of: a) obtaining a drill-bit with a longitudinal axis and first and second axially spaced ends, the drill-bit having a central portion and a plurality of blades protruding radially from the central portion; and b) turning the drill-bit around the longitudinal axis in a first direction so that the blades each advances in a circumferential direction, with a circumferentially facing leading portion on each blade first, while pulling the drill-bit axially, with the first drill-bit end in a leading direction, through the hard ground structure to thereby cause discrete cutters to cut the hard ground structure as the drill-bit is pulled to form the hole in the hard ground structure. Each blade has a first blade end, a second blade end, a first end portion, a second end portion, and a middle portion. The first end portion extends from the first blade end to the middle portion. The middle portion is disposed between the first end portion and the second end portion. The second end portion includes the second blade end and extends from the middle portion towards the second end of the drill-bit. The circumferentially facing leading portion of each blade has at least one of the discrete hard cutters placed thereat.

In one form, the discrete hard cutters are polycrystalline diamond cutters.

In one form, the at least one discrete hard cutter on each blade is on the first end portion of each blade.

In one form, there are a plurality of the discrete hard cutters on the first end portion of each blade.

In one form, the circumferentially facing leading portion of each blade has a curved shape between the first and second blade ends.

In one form, the discrete hard cutters each has a cutting edge. The cutting edges on each blade are arranged to cooperatively extend in a curved shape.

In one form, the middle portion of each blade has a radially outwardly facing surface that is substantially parallel to the longitudinal axis.

In one form, a discrete hard element is fixed at the radially outwardly facing surface of each blade to provide wear resistance.

In one form, the drill-bit has at least a one nozzle between adjacent blades. The method further includes the step of directing a fluid under pressure through the at least one nozzle to clear foreign matter from between the adjacent blades.

In one form, the step of turning the drill-bit while pulling the drill-bit consists of turning the drill-bit while pulling the drill-bit with a component that is threadably engaged with the drill-bit at one of the axially spaced ends of the drill-bit.

In one form, the other of the axially spaced ends of the drill-bit is threaded to engage a component usable to advance the drill-bit axially.

In one form, the at least one discrete hard cutter on each blade is on the second end portion of each blade.

In one form, each blade defines an edge at the circumferentially facing leading portion. At least one discrete hard cutter extends radially outwardly beyond the edge.

In one form, the at least one discrete hard cutter has a rounded cutting corner.

In one form, the at least one discrete hard cutter has a cylindrical shape.

In one form, the drill-bit has a radial dimension and an axial dimension. The axial dimension is greater than the radial dimension.

In one form, the axial dimension is not greater than 1.5 times the radial dimension,

In one form, the axial dimension is on the order of 1.2 times the radial dimension.

BRIEF DESCRIPTION OF THE DRAWINGS

FIGS. 1A to 1C illustrate examples of traditional drill bits;

FIG. 2A is a side view of a drill-bit in accordance with an embodiment;

FIG. 2B is side view image of an exemplary drill-bit;

FIG. 3A is a top view of the drill-bit of FIG. 2A showing an upper connection;

FIG. 3B is a top view image of an exemplary drill-bit in accordance with an embodiment;

FIG. 3C is a view of a bottom connection of the drill-bit opposite to the upper connection;

FIG. 3D is a side view of the drill-bit of FIG. 2A showing inner connection threads;

FIG. 4 illustrates an example of a PDC cutter in accordance with an embodiment;

FIG. 5 illustrates an example of a nozzle in accordance with an embodiment;

FIGS. 6A and 6B illustrate different views of a drill-bit including two rows of PDC cutters in accordance with an embodiment; and

FIGS. 6C and 6D illustrate different views of a drill-bit including three rows of PDC cutters in accordance with another embodiment.

It will be noted that throughout the appended drawings, like features are identified by like reference numerals.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT

The embodiments are drill-bits for making holes in a hard structure such as a rock. The drill-bit preferably has no moving parts and achieves both rigidity and a fast rate of penetration into rocks. In an embodiment, the drill-bit has a cone-shaped central portion with a plurality of blades/ribs (hereinafter, “blades”) protruding from the central portion. The blades are curved along a direction of a longitudinal axis of the cone to facilitate insertion into a hole when turned in a first direction, and exit from the hole when turned in a second direction opposite the first direction. Each blade has a plurality of discrete polycrystalline diamond cutters (PDC) provided in a first position for cutting the hard structure as the drilling-bit rotates in the first direction, and a plurality of updrill PDC cutters provided in a second position for cleaning the hole. Discrete hard cutters other than PDC cutters are usable in place of, or together with, PDC cutters. For example, discrete tungsten carbide cutters might be used. This is but one example.

FIG. 2A is a side view of a drill-bit in accordance with an embodiment, and FIG, 2B is side view image of an exemplary drill-bit, Likewise, FIG. 3A is a top view of the drill-bit of FIG. 2A showing an upper connection, and FIG. 3B is a top view image of an exemplary drill-bit in accordance with an embodiment.

As shown in FIGS. 2A and 2B, the drill-bit 100 has a central portion defining a cone 101 and top and bottom connections 102 and 103 with inner threads 105a, 105b (as shown in FIG. 3D) at axial opposite ends AE1, AE2 of the drill-bit 100 for connecting to a drilling rig (DR). The drilling rig may be connected to either the top connection 102 or to the bottom connection 103. FIG. 3C is a view of the bottom connection 103 of the drill-bit opposite to the upper connection 102, and FIG. 3D is a three dimensional view of the drill-bit of FIG. 2A showing the inner threads 105a, 105b.

One or more up-drill PDC cutters 116 may be positioned for reverse drilling only to allow the drill to drill its way of the hole. In the example of FIG. 2A, the up-drill cutter 116 is provided between the gage pad 108 and the lower portion 112. The up-drill PDC cutters 116 serve to clean the hole as the drill-bit rotates in the opposite direction of the drilling rotation e.g. clockwise, to exit the hole because the reverse rotation makes the location of the up-drill cutter 116 as the main surface with the debris in the hole. The up-drill PDC cutters 116 are designed to assist in the swabbing of the hole. If there is any residual rock formation, the up drills will cut the rock as the bit is pushed or pulled in the swabbing process.

Referring back to FIGS, 2A and 2B, it is shown that the drill-bit has a plurality of blades/ribs 104 (3-9 blades or and preferably 5-6 blades for a regular hole) provided co-centrally around the connection 102 and projecting radially from the cone 101. In an embodiment, the blades are shaped and dimensioned to open the hole and advance upon being rotated from the hole. In the embodiment in FIG. 2A, the blades are slightly curved along the direction of the rotation axis RA so as to ensure a smooth penetration into the rock to open the hole when the rotation is clockwise, as viewed from above, and a smooth/easy exit from the hole when the drill-bit is pulled axially oppositely. Accordingly, the blades are shaped and dimensioned to facilitate penetration into the hole of the drill-bit as a result of the rotation of the drill-bit.

The blades may define a middle portion 108, an upper portion 110 adjacent the connection 102 and a lower portion 112 defining a ski slope and provided at the lower half of the cone 101 as shown in FIGS. 2A and 2B. In an embodiment, the ski slopes 112 end at the bottom 103 of the drill-bit 100 and do not extend past the latter as shown in FIGS. 2A and 2B.

In an embodiment, the blades 104 may also be curved along the Z axis and have different thicknesses along the Y axis and different widths along the X axis, In an embodiment, the width of the blades may increase as the thickness decreases and vice versa to maintain the rigidity of the blades beyond a certain level.

In an embodiment, the upper portion 110 of the blades 104 may include a plurality of discrete hard/Polycrystalline Diamond Cutters (aka PDC cutters) 114 for cutting the rock as the drill-bit 100 rotates to make the hole. For purposes of simplicity, the hard cutters 114 will be identified as PDC cutters, though the cutter construction is not limited to Polycrystalline Diamond, as noted above. The PDC cutters may be provided in a row at the leading edge/corner E of each blade which is the main point of contact between the drill-bit and the rock formation. The PDC cutters are shown as disc/cylindrical/tapered cylindrical shapes that have portions that project radially to beyond the edge E of each blade. The projecting portion has a rounded cutting corner RC. The blades may be dimensioned to have holes/pockets therein to receive the PDC cutters. The number of PDC cutters is generally determined based on the hardness of the rock that is being cut. FIG. 4 illustrates an example of a PDC cutter in accordance with an embodiment. As shown in FIG. 4, the PDC cutter 114 comprises a polycrystalline diamond (PCD) top layer 116 integrally sintered onto a tungsten carbide substrate using a high-pressure, high-temperature process. This layer combination allows consistent high drilling performance to be maintained. The polycrystalline diamond layer offers controlled wear and the retention of a sharp cutting edge. The tungsten carbide substrate provides a strong and tough support for the polycrystalline diamond layer while facilitating attachment to the drill-bit body.

The middle portion 108 (aka gage pad 108) of the blade may be substantially parallel to the Y axis for stabilizing the drill-bit while in the hole and also for defining and refining the inner surface of the hole. The different gage pads 108 of the different blades are concentrically provided around the rotation axis of the drill-bit to avoid deviation of the drill-bit to the left or the right or up or down while rotating within the hole.

The lower portion (aka ski-slope) 112 of the blade is designed for easier pushing of the bit as while swabbing the hole. Swabbing is necessary to make sure the bore is clean and free of rock debris left behind during the cutting process. The shape of the lower portion 112 helps the bit 100 not to get hung up on any debris left behind in the bore.

Referring back to FIGS. 2A and 2B, there is shown a plurality of nozzles 118 provided between adjacent blades. Accordingly, the cone 101 may be hollow at the center thereof to fluidly connect a drilling pipe DP connected to the top connection 102 or the bottom connection 103 for providing the nozzles with a stream of fluid/water from a pressurized fluid/water source S outside the hole. A plug P may be provided at the bottom portion 103 or top portion 102 of the drill-bit 100 (depending on which end of the drill-bit the pipe is connected to) for preventing the water/fluid from running there through, thereby forcing the water flowing through the pipe to exit from the nozzles 118.

FIG. 5 illustrates an example of a nozzle in accordance with an embodiment. The nozzles 118 are located between the blades and positioned to clean the PDC cutters and/or the blades using a water stream injected under pressure out of the nozzles 118. For instance as shown in FIGS, 2A and 2B, the nozzles may be provided in proximity of at least the upper portion 110 and the gage pad 108 since these portions have a higher thicknesses when compared to the lower portion 112 and therefore, debris is more likely to accumulate at these portions rather than the lower portion 112.

In operation, as the drill-bit 100 is rotated by the drive component DC in the direction indicated by the arrow A (in a right-handed clockwise direction as viewed axially from above), the drive component DC is controlled to apply the appropriate amount of pull pressure to the bit 100 in the direction of the arrow D1, substantially parallel to the axis RA. The PDC cutters scrape the formation, and drilling fluid may then carry the cuttings through the bore hole back to the surface, and into a pit. There the cuttings are collected, run through a shaker, and drilling fluid may be pumped back through the drilling rig and back through the drilling rods and back through the bit. This recirculation may continue throughout the boring process.

An appropriate component C1 may be engaged with the threads 105b and operated to draw the drill-bit axially oppositely to the direction D1 as to set the drill-bit 100 preparatory to being pulled and turned for hole formation,

Accordingly, the embodiments describe a drilling bit which has no moving parts, and thus, it is less prone to failure and breaking in the hole. Testing has shown that the present drill-bit can achieve a rate of penetration (ROP) of at least 40%-60% higher than existing bits due in large part to the shape and structure of its blades. In some cases the increase in ROP was 5-7 times. A comparison was done in Hamilton, Tex. where a driller was penetrating the rock at 3-4 inches per minute with their cone cutter reamer. When they tested the drill-bit of the present invention (known as the DDI Volcano PDC Hole Opener/Reamer), their ROP increased to 3½ feet per minute. With respect to rigidity and failure rate, testing has shown that the present drill-bit has reduced the failure rate by 85%.

The higher rate of penetration is attributable to the fact that traditional “split bit” or cone cutter reamers pound and cut the formation using moving parts, while the present drill-bit scrapes and cuts the formation as the entire bit rotates within the hole. The higher rate of penetration generally translates to savings in fuel and labor for the drilling companies and faster deliveries for the clients.

Another problem associated with the traditional hole openers is that each cone cutter is designed to cut different types of rock, and this becomes a problem when the bit transitions from one layer of rock formation to another i.e. from limestone to shale to clay to dirt. Since there does not exist a single cone cutter that is designed to cut rock formations of varying hardness, the driller is forced to choose the cutter type for the rock he/she thinks he/she will be in more than the others. This is a very difficult guessing game, because it is rare to have accurate geological data. In fact, it is more common to have incorrect data than to have correct data, if any at all. The ideal scenario for any driller is to have a bit that is capable of cutting all ground formations with equal effectiveness.

To address this problem, the drill-bit 100 may be coated with a layer of Tungsten Carbide to allow the drill-bit 100 to drill in formations with different hardness and without breaking and/or wearing quickly. In an embodiment, the thickness of the Tungsten Carbide may vary depending on the area on which it is being applied. For example, areas of the blade which are in higher contact with the debris during forward and backward drilling may have a thicker layer to improve their rigidity,

In an embodiment, to improve the rigidity of the drill-bit and decrease interruptions during the drilling process, one or more additional rows (or partial rows) of PDC cutters may be provided in the drill-bit parallel to or adjacent the main row of PDC cutters shown in FIGS. 2A and 2B. The additional rows may be provided in areas that sustain the most pressure and friction with the rock formation. In an embodiment, the additional rows of PDC cutters may be provided on the upper section of the blade adjacent the gage pad as exemplified in FIGS. 6A to 6D. FIGS. 6A and 6B illustrate different views of a drill-bit including two rows of PDC cutters in accordance with an embodiment, and FIGS. 6C and 6D illustrate different views of a drill-bit including three rows of PDC cutters in accordance with another embodiment.

As shown in FIGS. 6A and 6B, the drill-bit 140 has a plurality of blades. One or more of these blades comprise primary row of PDC cutters 142 provided at the edge of the blade, and a secondary row 144 of back-up PDC cutters provided parallel to and adjacent the primary row 142. The blade may include a first row of pockets for receiving the first row 142 of PDC cutters and a secondary row of pockets provided behind the first row of pockets. Similarly, FIGS. 6C and 6D illustrate a similar drill-bit 150 with three rows of PDC cutters: a main row 152, a second row 154 and a third row 154. Needless to say, four or more rows of PDC cutters may be included all depending on the thickness of the blade at the portion of the blade where the additional rows of PDC cutters are added.

Drilling equipment is manufactured worldwide with right-handed threads. Thus, cooperating threads on a drill-bit are made so that as the drive component DC (FIG. 2A) turns in its driving direction, as indicated by the arrow A, the connection between the drive component DC and drill-bit is tightened. This avoids inadvertent separation between the drive component DC and drill-bit in operation.

The drill-bit 100 depicted is actually configured specifically effectively for only pull-reaming, with the threads 105a engaged by the threads T on the drive component DC, by turning the drill-bit 100 around the rotational/longitudinal axis RA in the direction A while pulling the drill-bit 100 axially in the direction of the arrow D1. The turning of the drive component DC in this manner tightens the threaded connection of the drive component DC and drill-bit. Turning of the drive component DC in the driving direction causes the PDC cutters 114 at circumferentially facing leading portions LP of each blade to cut the hard ground structure to thereby form a hole/bore.

The PDC cutters 114 at each circumferentially leading portion LP cooperatively extend in a curved shape that preferably at least nominally matches the curvature of the leading portion LP. The curved shape of each blade 104 at the leading portion, and preferably the nominally matching curved shape of a trailing portion TP of each blade 104 is chosen to facilitate advancement through hard ground structure as the drill-bit is turned around the axis RA and an advancing axial force is applied.

As depicted, the axial dimension AD of the drill-bit 100 is greater than the radial dimension RD thereof. AD in one form is not greater than 1.5 RD. AD may be on the order of 1.2 times RD.

While preferred embodiments have been described above and illustrated in the accompanying drawings, it will be evident to those skilled in the art that modifications may be made without departing from this disclosure. Such modifications are considered as possible variants comprised in the scope of the disclosure.

Claims

1. A method of forming a hole in a hard ground structure, the method comprising the steps of: a) obtaining a drill-bit comprising: a central portion having a longitudinal axis and first and second axially spaced ends; anda plurality of blades protruding radially from the central portion, each blade having:a first blade end, a second blade end, a first end portion, a second end portion, and a middle portion,the first end portion extending from the first blade end to the middle portion,the middle portion disposed between the first end portion and the second end portion,the second end portion including the second blade end and extending from the middle portion towards the second end of the drill-bit; anda circumferentially facing leading portion,the circumferentially facing leading portion of each blade having at least one discrete hard cutter placed thereat; andb) turning the drill-bit around the longitudinal axis in a first direction so that the blades each advances in a circumferential direction, circumferentially facing leading portion first, while pulling the drill-bit axially, with the first drill-bit end in a leading direction, through the hard ground structure to thereby cause the discrete cutters to cut the hard ground structure as the drill-bit is pulled to form the hole in the hard ground structure.

2. The method of forming a hole in hard ground structure according to claim 1 wherein the discrete hard cutters are polycrystalline diamond cutters.

3. The method of forming a hole in hard ground structure according to claim 1 wherein the at least one discrete hard cutter on each blade is on the first end portion of each blade.

4. The method of forming a hole in hard ground structure according to claim 3 wherein there are a plurality of the discrete hard cutters on the first end portion of each blade.

5. The method of forming a hole in hard ground structure according to claim 1 wherein the circumferentially facing leading portion of each blade has a curved shape between the first and second blade ends.

6. The method of forming a hole in hard ground structure according to claim 4 wherein the discrete hard cutters each has a cutting edge and the cutting edges on each blade are arranged to cooperatively extend in a curved shape.

7. The method of forming a hole in hard ground structure according to claim 1 wherein the middle portion of each blade comprises a radially outwardly facing surface that is substantially parallel to the longitudinal axis.

8. The method of forming a hole in hard ground structure according to claim 7 wherein a discrete hard element is fixed at the radially outwardly facing surface of each blade to provide wear resistance.

9. The method of forming a hole in hard ground structure according to claim 1 wherein the drill-bit comprises at least a one nozzle between adjacent blades and further comprising the step of directing a fluid under pressure through the at least one nozzle to clear foreign matter from between the adjacent blades.

10. The method of forming a hole in hard ground structure according to claim 1 wherein the step of turning the drill-bit while pulling the drill-bit comprises turning the drill-bit while pulling the drill-bit with a component that is threadably engaged with the drill-bit at one of the axially spaced ends of the drill-bit.

11. The method of forming a hole in hard ground structure according to claim 10 wherein the other of the axially spaced ends of the drill-bit is threaded to engage a component usable to advance the drill-bit axially.

12. The method of forming a hole in hard ground structure according to claim 3 wherein the at least one discrete hard cutter on each blade is on the second end portion of each blade.

13. The method of forming a hole in hard ground structure according to claim 1 wherein each blade defines an edge at the circumferentially facing leading portion and the at least one discrete hard cutter extends radially outwardly beyond the edge.

14. The method of forming a hole in hard ground structure according to claim 1 wherein the at least one discrete hard cutter has a rounded cutting corner.

15. The method of forming a hole in hard ground structure according to claim 1 wherein the at least one discrete hard cutter has a cylindrical shape.

16. The method of forming a hole in hard ground structure according to claim 1 wherein the drill-bit has a radial dimension and an axial dimension and the axial dimension is greater than the radial dimension.

17. The method of forming a hole in hard ground structure according to claim 16 wherein the axial dimension is not greater than 1.5 times the radial dimension.

18. The method of forming a hole in hard ground structure according to claim 16 wherein the axial dimension is on the order of 1.2 times the radial dimension.